The mammalian lens has been shown to contain a variety of proteins which have the ability to inhibit specific degradative enzymes. These include inhibitors for RNase, DNase, trypsin and chymitrypsin. We believe that the synthesis of these proteins is induced during lens cell differentiation in order to protect the lens from autolysis. We intend to purify these inhibitors and study their interaction with both the crystalline enzymes and endogenous lens enzymes. These inhibitory proteins lose their activity in the lens nucleus. This may represent loss of activity with age. This may be a causative factor in cataract formation since the loss of these protective inhibitors due to aging or insult may lead to protein breakdown and a change in the protein-protein interactions. We intend to measure the levels of these inhibitor proteins in both normal and cataractous human lenses and to use the purified inhibitors as probes of cataractous lens chemistry.